In the chemical processing industry and especially in refineries for processing petro-chemicals and hydrocarbons, emission of volatile organic hydrocarbon fluids and volatile organic hydrocarbon gases into the atmosphere is, and has been, a problem. Volatile organic compound emission regulations are currently being drafted by the Environmental Protection Agency.
One leakage source of volatile organic fluids into the atmosphere is from some or all of the valves used in the processing apparatus. Most of these valves are constructed with stem packings, as well known in the valve art. To prevent or materially reduce fluid leakage along the valve stems, the packing is tightened against the stems. To operate the valves, the stems must be turned and this induces high frictional contact of the packing and the stems, making the valves difficult to operate.
Leakage of radioactive steam along the stems of valves used in nuclear steam power plants has also been an environmental problem. To control such leakage in nuclear steam power plants it has been suggested in U.S. Pat. No. 3,979,104 to use bellows seals in butterfly valves. In the arrangement described in this patent, a buffer layer of uncontaminated steam having a pressure higher than the pressure of the contaminated steam is introduced into a seal chamber outwardly of the seal faces and the bellows to insure zero leakage of the contaminated steam past the seal device.